Atmospheric highs drive asymmetric sea ice drift during lead opening from Point Barrow

Abstract

Abstract. Throughout winter, the winds of migrating weather systems drive the recurrent opening of sea ice leads from Alaska's northernmost headland, Point Barrow. As leads extend offshore into the Beaufort and Chukchi seas, they produce sea ice velocity discontinuities that are challenging to represent in models. We investigate how synoptic wind patterns form leads originating from Point Barrow and influence patterns of sea ice drift across the Pacific Arctic. We identify 135 leads from satellite thermal infrared imagery between January–April 2000–2020 and generate an ensemble of lead-opening sequences by averaging atmospheric conditions and ice velocity across events. On average, leads open as migrating atmospheric highs drive differing ice–coast interactions across Point Barrow. Northerly winds compress the Beaufort ice pack against the coast over several days, slowing ice drift. As winds west of Point Barrow shift offshore, the ice cover fractures and a lead extends from the headland into the pack interior. Ice west of the lead accelerates as it separates from the coast, drifting twice as fast (relative to winds) as ice east of the lead, which remains coastally bound. Consequently, sea ice drift and its contribution to climatological ice circulation becomes zonally asymmetric across Point Barrow. These findings highlight how coastal boundaries modify the response of the consolidated ice pack to wind forcing in winter, producing spatially varying regimes of ice stress and kinematics. Observed connections between winds, ice drift, and lead opening provide test cases for sea ice models aiming to capture realistic ice transport during these recurrent deformation events.

Spring 2021 sea ice transport in the southern Beaufort Sea occurred during coastal ice opening events

“…Spatial discontinuities develop in the sea ice velocity field as lead patterns open, delineating portions of the pack that lose and remain in contact with the coast. Previous studies have suggested that coastal lead opening events in the Beaufort Sea play an important role in winter ice transport by temporarily enhancing rates of wind-driven ice drift as the ice separates from the coast (Lewis and Hutchings, 2019;Jewell et al, 2023). In agreement with these observational findings, model simulations of an exceptional coastal lead opening event in winter 2013 showed that the event enhanced MYI export from the Beaufort Sea (Rheinlaender et al, 2022).…”

“…Several observational studies have identified changes in the rate and efficiency of winter sea ice transport in association with opening of leads in the Beaufort Sea (Lewis and Hutchings, 2019;Jewell et al, 2023). To evaluate change in ice motion, these studies often rely on satellite-derived sea ice drift products, which are typically available at daily temporal resolution.…”

“…Internal stresses are often transmitted from far-field sources, complicating predictions of ice drift from local wind forcing. March and April 2021 fell at the end of the consolidated season in the Beaufort Sea (Jewell et al, 2023), the several-month period each year from midwinter to early spring when the Beaufort ice cover remains mostly consolidated (reaching SICs near 100 %) and contiguous with the Alaskan and Canadian coastlines that bound the sea.…”

“…Leads recurrently open along the Alaskan and Canadian coasts of the Beaufort Sea during the consolidated season as passing weather systems drive changes in regional wind forcing (Eicken et al, 2006;Lewis and Hutchings, 2019;Jewell and Hutchings, 2023). Spatial discontinuities develop in the sea ice velocity field as lead patterns open, delineating portions of the pack that lose and remain in contact with the coast.…”

Seasonal Evolution of the Sea Ice Floe Size Distribution from Two Decades of MODIS Data

“…In the late winter and spring, the Beaufort has high sea ice concentration. As external stresses, such as wind stress, are applied to the ice pack, the ice pack experiences strain, leading to fracture in a preferential direction that depend on the force's orientation relative to the coast (Lewis and Hutchings, 2019;Jewell et al, 2023). When we examine the newly fractured floes during this time period, we find a low variability in their orientation (Fig.…”